It is well known in the petroleum industry that after a bore hole has been completed, there are occasions when corrosive fluids in the bore hole must be kept out of contact with the well pipe casing because of the rapid destruction of the well pipe casing and the inability to replace the casing either practically or economically. In order to protect that portion of the well casing that is immersed in such fluids, well packers have been developed which are lowered down the well casing to a given point and then set in the casing so as to cause a fluid seal in the casing, sealing off that portion of the corrosive fluid below the packer from the well casing above the packer. Since the drill string extends through the packer to the portion of the well fluid below the packer, fluids can be pumped through the well string to the surface through the drill string, thus protecting the well casing from the corrosive fluids.
Well packers are associated with a cylindrical mandrel attached to the lower end of the drill string. The mandrel is inserted through the hollow well packer and has formed on each side thereof a J-shaped slot which engages a gudgeon pin in the surrounding anchor cage that forms a part of the well packer. The anchor cage also has spring loaded friction pads spaced around the outside thereof, generally 90.degree. apart, which engage the inside of the well casing and temporarily hold the well packer in a fixed position with respect to the well casing. The friction pads can support 200-300 pounds of weight without sliding. A gudgeon pin attached to and extending through opposite sides of the anchor cage engages a corresponding one of the J-slots. When the gudgeon pin is in the bottom portion of the J-slot, it is trapped and, by forcing the drill string downward, the packer is forced down into the well casing sliding the friction pads along the inside surface thereof.
When the proper depth at which the packer is to be set is reached in the bore hole, the friction pads hold the packer while the drill string is lifted slightly which releases each gudgeon pin from its trapped position at the bottom of the J-slots. By rotating the drill string slightly, the gudgeon pin is moved into the vertical section of the J-slot. The drill string can then be let down and the gudgeon pin travels upwardly in the J-slot. Forming a part of the mandrel, on the external surface thereof, is a band of threads or teeth. In like manner, on the anchor cage which contains the gudgeon pins are several arcuate segments of gear teeth that are urged inwardly against the mandrel by a resilient device such as a spring or springs. As the mandrel moves downwardly through the packer, the ratchetable teeth on the anchor cage slide over the band of teeth on the mandrel. The teeth are ratchetable in only one direction. As the mandrel moves downwardly with respect to the packer (which is being held in place by the friction pads) the teeth can ratchet with respect to each other. When the teeth are securely caught in locked engagement, the drill string is then pulled upwardly. A series of pivotable locking teeth in the anchor cage are forced outward against the well casing by a cam. These teeth are angled so as to prevent the anchor cage from moving downwardly in the well casing but not upwardly. As the mandrel continues to move the anchor cage upwardly, elastomer seals on the packer are compressed and a second cam on the upper side of the seals forces another set of locking teeth outwardly into the well casing to prevent upward movement of the slip in which the upper teeth are mounted. Continued upward movement of the drill string compresses the entire unit because the upper slip is now anchored by the locking teeth therein and will not move further upwardly. The lower teeth are engaged with the casing and will not allow the packer to move downwardly. The elastomer seals are compressed outwardly to engage the well casing and a fluid-tight seal is formed which prevents fluid below the packer from entering the well casing above the packer. Fluid in the well casing below the packer can be taken to the surface through the mandrel and the drill string.
When it is desired to remove the packer, the drill string has to be rotated in order to thread the latching teeth on the anchor cage off of the fixed teeth on the mandrel. Thus, it requires a considerable number of revolutions of the drill string to thread the anchor cage ratchetable teeth off the fixed mandrel teeth and, if the drill string should for any reason slip downwardly during the rotation, the ratchetable teeth simply slip over or ratchet across the fixed teeth on the mandrel and the process has to be started again.
The present invention overcomes the disadvantages of the prior art by limiting the teeth on the mandrel to an arcuate width of approximately 60.degree. on opposing sides of the mandrel circumference. In like manner, the ratchetable teeth on the anchor cage also have an arcuate width of approximately 60.degree.. The two sets of teeth operate in the normal fashion to latch so that the ratchetable teeth slide over the teeth on the mandrel when the mandrel is being lowered. Again, when the mandrel is pulled upwardly the teeth lock together holding the mandrel securely to the packer and allowing the packer to be set in place in the well casing as described earlier. When it is necessary to remove the packer however, the drill stem is simply rotated no more than one-quarter of a turn which moves the 60.degree. segment of teeth on the mandrel out of contact with the 60.degree. segment of ratchetable teeth on the anchor cage thus releasing the mandrel from the packer and allowing the mandrel to be pulled upwardly to disengage the packer from the sidewalls of the casing in the usual fashion.
The mandrel not only has the 60.degree. segment of teeth on opposing sides thereof, but also has a J-slot below, and spaced from, the mandrel teeth to receive the gudgeon pin on the anchor cage. The J-slot is formed on diametrically opposing sides of the mandrel surface. The bottom end of the J-slots traps the anchor cage gudgeon pins, as in the prior art, so that the entire packer assembly can be forced down into the well casing against the resistance of the friction pads by downward movement of the mandrel on the end of the drill string. The vertical section of each J-slot has an upper portion and a lower portion with the upper portion being wider than lower portion. The upper portion is coupled to the lower portion by a first sloping shoulder on one side of the J-slot. The bottom end of the J-slot is coupled to the lower portion of the J-slot by a second sloping shoulder substantially parallel to the first sloping shoulder. The ratchetable arcuate segments of teeth on the anchor cage are mounted on opposed sides of the anchor cage above and arcuately spaced from the gudgeon pins such that when the gudgeon pins are in the bottom end of the J-slot, the anchor cage arcuate segments of teeth are received by the vertical J-slot in the area adjacent the first sloping shoulder. When the mandrel is rotated to move the gudgeon pins from the bottom end of the J-slot to and in alignment with the lower vertical portion of the J-slot, the gudgeon pins move up the second sloping shoulder thereby rotatably moving the anchor cage which carries the ratchetable segments of teeth and causes them to move upwardly and rotatably parallel to the first sloping shoulder to a position in vertical alignment with the mandrel 60.degree. segments of teeth such that when the mandrel is subsequently lowered, the anchor cage arcuate segments of teeth ratchetably engage corresponding ones of the mandrel arcuate segments of teeth to secure the mandrel to the packer housing through the anchor cage.
The gudgeon pin moves up into the widest upper portion of the J-slot as the mandrel is lowered and the segments of teeth on the anchor cage engage the teeth segments on the mandrel. The gudgeon pin is then in a position such that when the mandrel is rotated one-quarter turn to disengage the arcuate segments of teeth, the gudgeon pin is enabled to move from one side of the widest portion of the J-slot to the other side. When the mandrel is raised, after the segments of teeth have been disengaged, the first sloping shoulder in the J-slot engages the associated gudgeon pin to rotate the anchor cage and bring the ratchetable arcuate segments of teeth thereon under and in vertical alignment with the corresponding arcuate segments of teeth on the mandrel. As the mandrel continues to be raised, the second sloping shoulder engages the gudgeon pin to further rotate the anchor cage and force the gudgeon pins into the bottom portion of the J-slot to carry the packer assembly as the mandrel is raised by the drill string. The anchor cage segments of ratchetable teeth are now in their original position in the J-slot adjacent the first sloping shoulder. The packer can now be removed from the well or reset as desired.
Thus, it is a primary object of the present invention to provide an improved well packer assembly which enables the mandrel to be disconnected or disengaged from the packing assembly simply by rotating the drill string one-quarter of a turn.
It is also an important object of the present invention to provide an improved latching assembly for releasably attaching a hollow well packer to an elongated tubular mandrel to enable the packer to be releasably set in fixed engagement with the well casing and released therefrom simply by rotating the drill string no more than one-quarter of a turn.
It is still another important object of the present invention to provide a latching assembly for a well packer and mandrel that has at least one arcuate section of fixed teeth integrally formed on the mandrel and at least one arcuate segment of ratchetable teeth mounted on the well packer such that when the mandrel is moved longitudinally in one direction with respect to the packer the segment of teeth on the anchor cage slides or ratchets over the fixed section of teeth on the mandrel to enable the packer to be set in the well casing, but fixedly engages the fixed section of teeth when the mandrel is moving longitudinally in the opposite direction with respect to the packer to rigidly attach the packer to the mandrel. However, the mandrel is allowed to be disengaged from the packer simply by rotating the drill string and mandrel one-quarter turn to release the ratchetable segment of teeth from the fixed section.
It is still another object of the present invention to provide a novel J-slot on diametrically opposed sides of the mandrel to receive a gudgeon pin on the anchor cage to move the anchor cage rotatably to align the ratchetable teeth on the anchor cage with the fixed sections of teeth on the mandrel and to receive the gudgeon pin when the drill string has been rotated a one-quarter turn to disengage the mandrel from the anchor cage and allow the gudgeon pin to be guided back into the J-slot so as to properly position the anchor cage for connection to the mandrel to enable removal of the well packer from the well casing.